From 6ef5add5dc07237e3db83d19770bba3c2bf6d386 Mon Sep 17 00:00:00 2001
From: Claude <noreply@anthropic.com>
Date: Thu, 20 Aug 2026 06:33:11 +0000
Subject: [PATCH] Close non-last parameter types of function templates

`FunctionTemplateTypeBuilder::build` gave a non-last parameter's type the
scope of the parameters before it. Nothing in that type carries a template
except an enum's type arguments, which `TemplateTypeBuilder::build` refines
via `build_refined`; for a parameter whose type contains a generic enum the
scope therefore leaked into the resulting type and left it open.

`BasicBlockType::params` holds the enclosing function's arguments, and
`analyze::basic_block` instantiates each of them against the caller's
variable through `assert_closed`. A generic enum in any parameter but the
last one thus aborted with "unexpected variable" as soon as the body had a
block needing its own precondition.

Build such a parameter without the scope, as the last parameter's own type
is already built inside `build_refined`.

Fixes #235

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01T3XpZ2MXjgs3JoodCr8iA9
---
 src/refine/template.rs              |  4 ++--
 tests/ui/fail/option_param_order.rs | 15 +++++++++++++++
 tests/ui/pass/option_param_order.rs | 14 ++++++++++++++
 3 files changed, 31 insertions(+), 2 deletions(-)
 create mode 100644 tests/ui/fail/option_param_order.rs
 create mode 100644 tests/ui/pass/option_param_order.rs

diff --git a/src/refine/template.rs b/src/refine/template.rs
index 3419ae67..246688cc 100644
--- a/src/refine/template.rs
+++ b/src/refine/template.rs
@@ -625,8 +625,8 @@ where
                         rty::RefinedType::unrefined(
                             self.inner
                                 .for_template(self.registry)
-                                .with_scope(&builder)
-                                .build(param_ty.ty),
+                                .build(param_ty.ty)
+                                .vacuous(),
                         )
                     }
                 });
diff --git a/tests/ui/fail/option_param_order.rs b/tests/ui/fail/option_param_order.rs
new file mode 100644
index 00000000..ff668922
--- /dev/null
+++ b/tests/ui/fail/option_param_order.rs
@@ -0,0 +1,15 @@
+//@error-in-other-file: Unsat
+//@compile-flags: -C debug-assertions=off
+
+fn get_or(o: Option<i64>, d: i64) -> i64 {
+    match o {
+        Some(x) => x,
+        None => d,
+    }
+}
+
+fn main() {
+    assert!(get_or(Some(1), 9) == 1);
+    // `get_or` returns the default in the `None` case, so this assertion does not hold
+    assert!(get_or(None, 9) == 1);
+}
diff --git a/tests/ui/pass/option_param_order.rs b/tests/ui/pass/option_param_order.rs
new file mode 100644
index 00000000..468f5b8f
--- /dev/null
+++ b/tests/ui/pass/option_param_order.rs
@@ -0,0 +1,14 @@
+//@check-pass
+//@compile-flags: -C debug-assertions=off
+
+fn get_or(o: Option<i64>, d: i64) -> i64 {
+    match o {
+        Some(x) => x,
+        None => d,
+    }
+}
+
+fn main() {
+    assert!(get_or(Some(1), 9) == 1);
+    assert!(get_or(None, 9) == 9);
+}